The invention relates to an operating mechanism of a multipole switch capable of occupying three distinct stable positions, notably a first closed position, a second intermediate open position, and a third ground or earthed position, said mechanism being of the tumbler type comprising:
an energy storage spring associated with a toggle with highspeed dead-point overshoot, fitted with an actuating lever articulated on a spindle of a first operating crank,
a main operating crank fixed on a rotating shaft securedly fixed to the movable assembly of the switch,
an earthing crank mounted with limited rotation on a first operating spindle between an inactive position when the main crank is moved by the toggle between the closed and open positions, and an active earthed position causing the bearing point and the line of action of the spring to be modified resulting in further rotation of the main crank beyond the open position to the earthed position,
and locking means of the main crank in each of the three positions of the switch.
A known mechanism includes a single energy storage spring which is described in detail in French Patent No. 2,500,222 filed by the applicant (and having an English language equivalent as European Patent 58,585). A single energy storage spring is sufficient to actuate the switch in one of the three positions. The opening and closing operating spindle is formed by the shaft of the movable assembly drive lever operating cam. The toggle actuating lever is arranged between the operating cam shaft, and the earthing crank operating spindle. This results in a lateral protrusion of the operating lever when it is engaged on one of the two operating spindles. The operating cam is unlocked after the toggle deadpoint has been overshot due to the reactive force of a ramp on a block of a spring-mounted retaining crank. The ramp and springmounted retaining crank assembly does not provide positive latching of the cam, since unlocking takes place when the driving torque of the cam actuated by the toggle outweighs the resisting torque of the retaining crank.
The object of the invention is to achieve a compact operating mechanism, with positive latching of the operating crank.